1. Field of the Invention
The present invention relates to a process system for forming a resist film on a semiconductor wafer and developing an exposed resist film.
2. Description of the Related Art
In a photo-resist step of a semiconductor fabrication process, a resist is coated on the front surface of for example a semiconductor wafer (hereinafter referred to as wafer). As a result, a resist film is formed. After a pattern is exposed on a wafer, with a developing solution, a developing process is performed. To perform such a process, a coating and developing process system is used.
In the coating and developing process system, various units are used. For example, a unit that coats a resist on a wafer, a unit that supplies a developing solution to the wafer that has been exposed, a unit that cools the wafer, and a unit that heats the wafer are used. In addition, a conveying unit that transfers a wafer among these units is disposed.
To compactly structure the coating and developing process system, a vertical conveying unit that conveys a wafer in the vertical direction and the direction is disposed at a center portion of the system. A plurality of multi-staged unit blocks are disposed around the conveying unit.
However, such a coating and developing process system cannot be dynamically expanded or reduced. In other words, to expand such a system, the number of stages of units or the number of unit blocks can be increased. However, it is impossible to dynamically expand the system for example two times or three times. Thus, conventionally, to dynamically expand the system, for example, the number of coating and developing process systems are increased.
When the number of units of the system is increased, the following problem will take place. In other words, in the coating and developing process system, a substrate loading/unloading portion is disposed between process stations each of which is composed of a unit block and a conveying unit. The substrate loading/unloading portion is composed of for example an interface portion that transfers a wafer between a cassette station and an exposing unit. The cassette station loads and unloads a cassette accommodating many wafers with an AGV (Automatic Guided Vehicle). Thus, when the number of units of the system is increased, the number of substrate loading/unloading portions is increased. However, since the process performance of the entire system depends on the process performance of each process station, the expanded substrate loading/unloading portions become redundant.
In addition, in such a coating and developing process system, unit blocks are disposed around a conveying unit. Thus, it is difficult to perform a maintenance work for the conveying unit.